1. Field of the Invention
The present invention relates generally to the measurement of metabolism activity, and more particularly, to the measurement of an individual""s caloric energy balance.
2. Description of the Related Art
Many individuals are concerned with their body weight for reasons of health and personal appearance. Despite constant warnings by the media that excessive body weight and high body fat percentages are associated with such negative health factors as hypertension, heart disease and diabetes, and is thus detrimental to an individual""s well-being and life expectancy, an overall decrease in physical activity has resulted in an increasing number of overweight and often seriously obese individuals.
It is generally known that an individual""s body fat is related to caloric energy balance, which is the difference between caloric intake (calories consumed from food), and caloric expenditure (calories that are burned by base metabolism and physical activity). If an individual expends more calories than are consumed, he or she will lose fat. Conversely, if an individual expends fewer calories than consumed, he or she will gain fat. For a typical individual, a net positive or negative balance of 3,500 calories will cause, respectively, a gain or a loss of one pound of fat.
An effective way of controlling body fat is to monitor, on a regular basis, individual net caloric energy balance to establish an individual exercise regimen in which net caloric energy balance will be zero or negative. To aid in this process, various products have been developed and marketed that measure an individual""s daily caloric expenditure from the user""s rest or base metabolic rate and his or her level of physical activity. A product of this type is described in U.S. Pat. No. 5,749,372. Products have also been developed which allow an individual to keep track of daily or weekly caloric input.
Although presently-existing products theoretically provide a mechanism for predicting body fat percentage changes from caloric balance information, the accuracy of the prediction is quite poor. As a result, some individuals may lose weight, despite the fact that these prior art devices predict an increase in body fat percentages. Other individuals may be disappointed when these devices predict a decrease in body fat percentage, but no such change ever materializes. Major deficiencies in these products are their inabilities to, (1) account for changes in the user""s base metabolic rate (which typically occur during an exercise course that may include aerobic activity and weight training), (2) accurately monitor physical activity and (3) allow the convenient and accurate entry of caloric consumption information. As a result, presently existing caloric monitoring products produce erroneous indications of the individual""s base metabolic rate, activity calories expended and calories consumed, which in turn, produce erroneous measurements of caloric energy balance.
Thus, there is a need for an improved, more accurate device for measuring and monitoring an individual""s net caloric energy balance. There is also a need for a monitoring device, which considers variations in an individual""s body fat percentage over time.
A novel caloric energy balance monitor predicts changes in an individual""s body fat or body fat percentage based upon the individual""s caloric balance. Caloric balance is determined from an individual""s base metabolic rate, physical activity, and caloric consumption. To achieve increased prediction accuracy over time, the monitor calculates a correction factor by comparing predicted and actual changes in the individual""s body fat or body fat percentage. The monitor utilizes this correction factor in subsequent computations of caloric balance so as to more accurately predict subsequent changes in body fat or body fat percentage.
An individual""s base metabolic rate (BMR, in units of calories) is averaged over a period of time and then added to the calories expended during physical activity. BMR is indicative of calories that are burned by an individual at rest. Calories burned as a result of exercise as well as BMR are then subtracted from averaged caloric consumption. Caloric consumption is determined by the caloric content of foods consumed over a given time period. The result of this calculation provides an indication of a net caloric energy increase or decrease. This indication may then be integrated and averaged to compute a predicted change in body fat or body fat percentage.
The user""s current body fat percentage is compared to a known previous body fat percentage for the user so as to obtain the actual change in body fat percentage. That difference is used to calculate a correction factor, which is preferably integrated over a 24-hour period, converted to calories, and combined with the caloric input at the summer in subsequent computations of the predicted change in body fat percentage.
Thus, for example, if the predicted body fat percentage change over a period of one week were xe2x88x921/2%, and there was no actual change in the individual""s body fat percentage, then the correction factor would be 1/14% per day (1/2% error over 7 days). Since the conversion of xe2x80x9ca poundxe2x80x9d of body fat to calories is 3,500 calories, the correction factor would be 3,500/14 or +250 calories per day, spread or averaged over a 24-hour period. This correction factor is added to the of activity, rest and input calories to compute a subsequent value of predicted change in body fat percentage.
Pursuant to an illustrative embodiment of the invention disclosed herein, the individual""s estimated at xe2x80x9cbase metabolic ratexe2x80x9d (BMR) and current actual body fat percentage may be obtained from a body composition analyzer of the type disclosed in the above-referenced co-pending application. The base metabolic rate is a function of the individual""s fat-free mass, which may be computed in the body composition analyzer, using of any of several known algorithms, one of which is described in an article entitled, xe2x80x9cResting Metabolic Rate Is Lower In Women Than In Menxe2x80x9d, published in 1993 in the American Physioloical Society 0161-7567/93 at page 2514.